Automatic callback method for a packet-oriented network

ABSTRACT

In cases when a called participant (Tln-B) is not registered on a packet orientated network (IP-N), a call-back request made by a calling subscriber (Tln-A) is transmitted automatically to a substitutional device (ST-B) which is disposed in a network (IP-N) and assigned to the called subscriber (Tln-B). Preferably, the call-back request is stored in a separate data base (DB-B). As soon as the called subscriber (Tln-B) is registered in the network (IP-N), the call-back request is transmitted to the called subscriber (Tln-B) who carries out said request.

[0001] From the product publication “Sonderausgabe telcom report undSiemens Magazin Com: ISDN im Büro-HICOM” [Special edition of telcomreport and Siemens° Com magazine: ISDN in the Office HICOM] Siemens AG,Berlin and Munich, 1985, in particular from pages 14 to 31, acommunication system designed for information switching, in particularfor voice data switching, is known which supports a large number offeatures such as automatic callback, call pickup, call forwarding, etc.It is furthermore known from the 1991 product publication “HICOM 300Networking”, reference number A31001-W-A30, issued by the companySiemens AG, how to link up communication systems into a—generallyprivate—communication network and make features that are availablelocally on one communication system available throughout the network.The features are usually implemented across the network by means of anetworking protocol, specific to the communication system, that is basedon a timeslot-oriented transmission protocol.

[0002] This gives each subscriber of a communication system thepossibility of activating or deactivating features, such as an automaticcallback, on a network-wide basis. To do this the subscriber dials, forexample, a feature-specific service code and the directory number of theterminal for which the relevant feature is to be activated ordeactivated.

[0003] ITU-T (International Telecommunication Union) RecommendationH.450.9 describes a method for an implementation of the known “automaticcallback” feature in packet-oriented networks according to the H.323standard. Analogously to timeslot-oriented communication networks, adistinction is made here between two different cases:

[0004] 1) automatic callback in the event of a “busy” destinationsubscriber (CCBS) and

[0005] 2) automatic callback in the event of a “free” destinationsubscriber (CCNR).

[0006] A requirement of both variants is for the subscribers to beregistered on the network via their respective terminals. Besides thetwo statuses “busy” and “free”, in packet-oriented networks employingthe Internet Protocol—IP for short—there is another status in which thesubscriber is neither “busy” nor “free” but is “not registered”. This isthe case, for example, when an application implemented on the relevantterminal has not been launched or the terminal is inactive.

[0007] The object of the present invention is to specify a method bymeans of which the “automatic callback” feature can also be executed inpacket-oriented networks in cases where a called subscriber is “notregistered” on the network.

[0008] This object is achieved according to the invention with thefeatures of claim 1 or of claim 2.

[0009] In the event that a called subscriber—or the terminal assigned tothe called subscriber—is not registered on the packet-oriented network,then according to the invention a deputizing device frequently referredto in the relevant literature as a proxy—will assume the functions ofthe called terminal. The deputizing device is generally implemented as arelevant function in a data processing device. The deputizing deviceallows the calling subscriber to place an automatic callback requestwith the called subscriber. As soon as the called subscriber registerson the packet-oriented network from a terminal, the callback requestwill be transmitted to this terminal and so will be available forexecuting the automatic callback.

[0010] In cases where the called subscriber—or the terminal assigned tothe called subscriber—is registered on the network when a callbackrequest is activated by the calling subscriber but de-registers from thenetwork before the callback is executed, the callback request willautomatically be stored in the network (IP-N). As soon as the calledsubscriber re-registers on the network, the callback request will betransmitted to the called subscriber and executed by that subscriber.

[0011] A major advantage of the method according to the invention isthat it can easily be implemented in existing systems.

[0012] A further advantage of the method according to the invention liesin the called subscriber's ability to register from any terminal in thepacket-oriented network, with the callback request being transmitted tothe terminal on which the called subscriber has registered so thatmobility required for the subscribers can be provided by simple means.

[0013] Advantageous developments of the invention are described in thesubclaims.

[0014] An advantage of embodiments of the invention defined in thesubclaims consists, among other things, in the fact that old and thusgenerally no longer current requests are automatically removed from thesystem through the cancellation of callback requests on expiration of aperiod of time that can be pre-specified, thereby minimizing the load onthe system due to monitoring of the callback requests.

[0015] An exemplary embodiment of the invention is described in thefollowing with the aid of the drawing.

[0016]FIG. 1: shows a block diagram for schematically representing themain functional units involved in the method according to the invention;and

[0017]FIG. 2: shows a flowchart for elucidating the main process stepsthat take place within the method according to the invention.

[0018]FIG. 1 shows a first and a second zone Z-A, Z-B which areinterconnected via a packet-oriented network IP-N, for example a LocalArea Network (LAN for short). Data is transmitted between the zones Z-A,Z-B over the packet-oriented network IP-N by means of the H.323 andH.225 standards known per se of the ITU (International TelecommunicationUnion).

[0019] A zone Z-A, Z-B in each case comprises what is called agatekeeper GK-A, GK-B and several devices assigned to this gatekeeperGK-A, GK-B. Shown by way of example for each zone Z-A, Z-B is a terminalEGA, EG-B assigned to a subscriber Tln-A, Tln-B, a deputizing deviceST-A, ST-B, and a database DB-A, DB-B. Several zones are in turncombined into what is called a domain (not shown). A terminal EG-A, EG-Bcan be, for example, what is called an ‘IP-Phone’ or a ‘personalcomputer’ with a suitable application running on the personal computer.

[0020] Several terminals are usually assigned to a zone Z-A, Z-B, withthe deputizing device ST-A, ST-B, the database DB-A, DB-B, and thegatekeeper GK-A, GK-B being assigned in this case jointly to theterminals. The deputizing device ST-A, ST-B, the database DB-A, DB-B andthe gatekeeper GK-A, GK-B of a zone Z-A, Z-B can be either is separatedevices or a number of units combined into a single device. What isessentially performed by the gatekeeper GK-A, GK-B of a zone Z-A, Z-B isregistration of the devices assigned to it and bi-directional addressconversion between what are called alias addresses employed within azone Z-A, Z-B and the addresses required by the packet-oriented networkIP-N for connection setup. An alias address can be, for example, atelephone number or an e-mail address used by a subscriber Tln-A, Tln-Bfor a connection setup.

[0021] In the present exemplary embodiment the terminals EG-A, EG-Bassigned to the subscribers Tln-A, Tln-B are in each case assigned todifferent zones Z-A, Z-B. The subscribers Tln-A, Tln-B or the terminalsEG-A, EG-B can, however, also be assigned to a common zone Z-A, Z-B or acommon domain.

[0022] In the present embodiment of the invention a connection setup isinitiated proceeding from a first subscriber Tln-A registered on thefirst gatekeeper GK-A of the first zone D-A to a second subscriber Tln-Bof the second zone Z-B. This connection setup can be a voice connection,a video connection or a multimedia connection. The exemplary embodimentis based on the assumption that all calls to the second subscriber Tln-Bare routed via the second gatekeeper GKB. It is of no significance forthis exemplary embodiment whether the calls from or to the firstsubscriber Tln-A are or are not routed via the first gatekeeper GK-A.

[0023]FIG. 2 shows a flowchart for elucidating the main messages thatare exchanged by means of the method according to the invention. Theunbroken thick arrows here represent a connection setup message forestablishing a connection to a useful-data channel, the unbroken thinarrows represent a signaling message, the dot-dash arrows represent amessage according to the known H.225.0 RAS protocol of the ITU, and thedotted arrows represent a database protocol message.

[0024] In the present exemplary embodiment the first terminal EG-A sendsa connection setup message “SETUP” to the second gatekeeper GK-Baccording to the H.323 standard. The first terminal EG-A canalternatively also transmit the connection setup message “SETUP” to thefirst gatekeeper GK-A, which forwards the connection setup message“SETUP” to the second gatekeeper GK-B. The second gatekeeper GK-Bdetermines whether the second subscriber Tln-B is currently registeredon the second gatekeeper GK-B. If this is not the case, the secondgatekeeper GK-B will forward the received connection setup message“SETUP” to the second deputizing device ST-B. The second deputizingdevice ST-B then functions as a deputy for the second terminal EG-B andsends a message “ALERTING” according to the H.225.0 standard back to thefirst terminal EG-A.

[0025] On receipt of the message “ALERTING”, the first terminal EG-A isset to a status in which the feature “automatic callback on free” can beinitiated on the first terminal EG-A according to the H.450.9 standard.For this, a new signaling connection containing the H.450.9 operation“ccnrRequest.Invoke” in a signaling message “SETUP” according to theH.225.0 standard is set up between the first terminal EG-A and thesecond gatekeeper GK-B. This signaling message “SETUP” is, aspreviously, forwarded from the second gatekeeper GK-B to the seconddeputizing device ST-B. The operation “ccnrRequest.Invoke” contains thedirectory number of the first subscriber Tln-A, the directory number ofthe second subscriber Tln-B and, optionally, a callback identifier andinformation about the required service type (voice, video, multimedia, .. . ). This data will be referred to below as callback data.

[0026] The second deputizing device ST-B accepts the callback request ofthe first subscriber Tln-A and sends an acknowledgement message “RELEASECOMPLETE” according to the H.225.0 standard together with an operation“ccnrRequest.ReturnResult” according to the H.450.9 standard back to thefirst terminal EG-A. On receipt of the acknowledgement message “RELEASECOMPLETE”, the first terminal EG-A releases the still existingconnection of the original connection setup in the alerting status withthe message “RELEASE COMPLETE” according to the H.225.0 standard.

[0027] In an ensuing step, the second deputizing device ST-B transmitsthe callback data to the second database DB-B, in which the callbackdata is buffered. The second database DB-B can be physically located onthe same device on which the second deputizing device ST-B has beenimplemented. Any database protocol, such as ODBC, JDBC, XML, . . . , canbe used as the interface and protocol between the second deputizingdevice ST-B and the second database DB-B.

[0028] If the second subscriber Tln-B registers on the second gatekeeperGK-B within a period of time that can be pre-specified—within 24 hours,for example—communication will take place between the second terminalEG-B and the second database DB-B. The period of time can be monitoredin the first terminal EG-A by, for example, what is called an “SS-CCservice duration timer” according to the H.450.9 standard. Alongsideother information—the user profile, for example—the second database DB-Bthen also transmits information about any outstanding callbacks, i.e.the callback data, to the second terminal EG-B.

[0029] The second terminal EG-B is then able to execute the callbackprocedure according to the H.450.9 standard. In the present exemplaryembodiment this is effected by sending an availability operation“ccExecPossible.Invoke” to the first terminal EG-A as part of asignaling message “SETUP” according to the H.225.0 standard. It isassumed in the present exemplary embodiment that all calls to or fromthe second subscriber Tln-B are routed via the second gatekeeper GK-B.In the present exemplary embodiment the first terminal EG-A isregistered on the first gatekeeper GK-A and has the status “free”. Thefirst subscriber Tln-A is called locally from the first terminal EG-Aand the signaling connection between the first terminal EG-A and thesecond terminal EG-B is released from the first terminal EG-A by thesignaling message “RELEASE COMPLETE”.

[0030] If the first subscriber Tln-A answers, this will result in theactual “automatic callback” from the first terminal EG-A to the secondterminal EG-B in the form of a connection setup according to the H.323and H.450.9 standards by means of a connection setup message “SETUP”,which contains an H.450.9 operation “ccRingout.Invoke”. If the secondsubscriber Tln-B answers, connection setup messages “ALERTING” and“CONNECT” according to the H.225.0 standard will be transmitted from thesecond terminal EG-B to the first terminal EG-A. The connection setupmessages “SETUP, “ALERTING”, and CONNECT” contain information (notshown) needed in order to set up the useful-data channels according tothe H.323 standard.

[0031] Transmission of the callback data by the second deputizing deviceST-B to a second database DB-B makes it possible for the secondsubscriber Tln-B to register on the second gatekeeper GK-B from anyterminal and for the callback to proceed nonetheless to its furtherimplementation. This is facilitated by transmission of the callback datastored in the second database DB-B to the terminal on which the secondsubscriber Tln-B registers. The method according to the invention thusalso provides a required mobility for the subscribers Tln-A, Tln-B.

[0032] According to a further embodiment of the invention, the secondsubscriber Tln-B is registered on the second gatekeeper GK-B when thecallback request is activated by the first subscriber Tln-A. In thiscase, the callback data according to the H.450.9 standard will be storednot in the second deputizing device ST-B but in the second terminalEG-B. If, however, the callback is not executed because the secondsubscriber Tln-B has de-registered from the second gatekeeper GK-B, thenproceeding from the second terminal EG-B the callback data will betransmitted to the second database DB-B. When the second subscriberTln-B re-registers on the second gatekeeper GK-B, the callback data willbe transmitted again to the terminal via which the second subscriberTln-B has currently registered and the “automatic callback” will beexecuted as described above.

[0033] According to yet a further embodiment of the invention, the firstsubscriber Tln-A is not registered on the first gatekeeper GK-A when thecallback is executed. If this is the case, then the first deputizingdevice ST-A of the first domain D-A will, together with the firstdatabase DB-A, assume the functions of the first terminal EG-A.

[0034] The first deputizing device ST-A will here respond to theavailability operation “ccExecPossible.Invoke” of the second terminalEG-B instead of the first terminal EG-A with the operation“ccSuspend.Invoke” according to the H.450.9 standard.

[0035] When the first subscriber Tln-A re-registers on the firstgatekeeper GK-A, the original callback request will be reactivated bymeans of an operation “ccResume.Invoke”. It is possible here to ask thefirst subscriber Tln-A, before the callback is executed, whether thecallback is still required. If the first subscriber Tln-A de-registers,the deputizing device ST-A will also assume the function of callbacktime monitoring from the first terminal EG-A and cancel the callbackrequest by means of an operation “ccCancel.Invoke” according to theH.450.9 standard if the period of time that can be pre-specified isexceeded.

[0036] In the above exemplary embodiments the method according to theinvention relates to H.323 communication networks. However, the methodcan also be used in other communication networks, for example in whatare called SIP communication networks.

1. Method for an automatic callback in a packet-oriented network (IP-N)wherein in cases where a called subscriber (Tln-b) is not registered onthe network (Ip-n) a callback request from the calling subscriber(Tln-a) is automatically transmitted to a deputizing device (St-b) thatis located in the network (Ip-n) and assigned to the called subscriber(Tln-b) and is stored by that device, and wherein as soon as the calledsubscriber (Tln-b) registers on the network (ip-n) the callback requestis transmitted to the called subscriber (Tln-b) and executed by thatsubscriber:
 2. Method for an automatic callback in a packet-orientednetwork (IP-N) wherein in cases where a called subscriber (Tln-B) isregistered on the network (IP-N) when a callback request is activated bya calling subscriber (Tln-A) but de-registers from the network (IP-N)before the callback is executed, the callback request will automaticallybe stored in the network (IP-N), and wherein as soon as the calledsubscriber (Tln-B) registers on the network (IP-N) the callback requestwill be transmitted to the called subscriber (Tln-B) and executed bythat subscriber.
 3. Method according to claim 1 or 2 characterized inthat the callback request is stored in a separate database (DB-B) andtransmitted from this to the called subscriber (Tln-B).
 4. Methodaccording to one of the claims 1 to 3 characterized in that the callbackrequest is automatically canceled on expiration of a period of time thatcan be pre-specified.
 5. Method according to claim 4 characterized inthat the expiration of the period of time is monitored by a terminalassigned to the calling subscriber (Tln-A).
 6. Method according to oneof the preceding claims characterized in that in cases where the callingsubscriber (Tln-A) is not registered on the network (IP-N) when thecalled subscriber (Tln-B) executes the callback, the callback requestwill be transmitted to a deputizing device (ST-A) assigned to thecalling subscriber (Tln-A).
 7. Method according to claim 6 characterizedin that in these cases the expiration of the period of time is monitoredby the deputizing device (ST-A) assigned to the calling subscriber(Tln-A).
 8. Method according to one of the preceding claimscharacterized in that a common deputizing device (ST-A, ST-B) isassigned to several subscribers.
 9. Method according to one of thepreceding claims characterized in that the registering of a subscriber(Tln-A, Tln-B) is monitored by a gatekeeper (GK-A, GK-B) assigned to therespective subscriber (Tln-A, Tln-B).
 10. Method according to one of thepreceding claims characterized in that a transmission of data over thenetwork (IP-N) is implemented by means of the H.225 and H.323 protocolsknown per se of the ITU.
 11. Method according to claim 10 characterizedin that the callback request is implemented by means of messages basedon the H.450.9 protocol known per se of the ITU.
 12. Method according toone of the claims 1 to 9 characterized in that a transmission of dataover the network (IP-N) is implemented by means of the SIP protocolknown per se.